1. Field of the Invention
The invention relates generally to semiconductor processing equipment and more specifically to mass flow controllers and other devices for the delivery and regulation of hazardous and non-hazardous semiconductor processing gases.
2. Description of the Prior Art
Various recipes are used in the fabrication of semiconductor devices. Such fabrication involves many discrete processing steps where a silicon wafer is cleaned, polished, oxidized, masked, etched, doped, metalized, etc. The steps used, there particular sequence and the materials involved all contribute to the making of particular devices.
Conventional semiconductor fabrication techniques depend on the use of particular process gases, some of which are hazardous. The fabrication of a single chip can require the careful synchronization and measured delivery of as many as a dozen gases to a reaction chamber. Mass flow controllers (MFC's) have long been used to deliver such gases in the required volumes to the point of use.
Conventional semiconductor processing gas systems allow a great deal of component flexibility in the choice of particular MFC's, valves, filters, etc. Weldment and stick manufacturing techniques associated with such prior art systems are well-understood and mastered. But such prior art systems amount to dumb boxes with dumb components that interact only one way with the process controller. Very often signals are sent to a conventional dumb gas box to open a valve and mass flow control the flow. No feedback is provided by the dumb gas box and the first acknowledgment from the system of flow is the all-too-late feedback from the reaction chamber. However, a few mass flow controllers do report back their flow.
Component failures in conventional gas box systems often lead to extensive downtimes. Whole fab lines can be affected with serious impact to production volumes. Switching out failed components can take considerable time because of the complex configurations and difficult access. Keeping a complete inventory of replacement parts on hand to minimize the mean-time-to-repair (MTTR) can be very costly. Worse, component failures are often misdiagnosed, leading to a lot of wasted time and effort. In situ diagnostic tools are generally non-existent.
In general, MFC's have proven to be the least reliable components in a processing gas delivery system. The gas boxes can very often become scapegoats for other equipment and process problems.